Visible and infrared imaging systems are useful in many applications such as, for example, in military applications to provide essential information relative to surveillance, remote observations, night vision, and guided weapons control as well as commercial applications for industrial, transportation, space and environmental use. Conventional imaging systems, however, generally provide only two-dimensional imaging, and many of the above military and commercial applications, require three-dimensional imaging. For these and other applications laser range finders have been used to augment conventional two-dimensional imagers by providing single-point ranging. However, the usefulness of these systems is limited, in that they are incapable of imaging multiple objects within a scene.
Scanning lidar systems are capable of imaging and ranging multiple objects within an image scene, but their response time is slow and is limited by the time it takes to rasterscan the full scene. Thus, these systems do not provide real time three-dimensional imaging. Other three-dimensional imaging systems utilize a stereoscopic technique which requires multiple cameras at multiple observation sights. These systems require a significant amount of hardware and are very costly. Yet another type of three-dimensional imaging system illuminates a scene to be imaged and uses the returned light intensity data to accomplish ranging of objects within the scene. However, variations in scene illumination are a major problem. Also since many objects have variations in reflectivity over their surfaces and different objects have different reflectivities, inaccuracies in ranging are common.